684 POPULAR SCIENCE MONTHLY. 



which can not account in any way for the regularities which have 

 been observed. From another source, partly physical and partly 

 chemical, the theory of the unity of matter has received strong 

 support, and this statement brings us to another of the greatest 

 discoveries made during the nineteenth century — that of the spec- 

 troscope and spectrum analysis. 



It was in 1860 that Kirchhoff and Bunsen added this new 

 weapon to the arsenal of scientific research. The spectroscope 

 itself, as an instrument, was an invention in the department of 

 optics, but its applications to chemistry were among the most ob- 

 vious and the most startling of its achievements. With its aid 

 new elements were discovered — rubidium, csesium, thallium, in- 

 dium, and gallium; in many lines of investigation it found imme- 

 diate use; but, more than all, it made possible the analysis of the 

 heavenly bodies, and proved that the same kinds of matter exist 

 throughout the visible universe. Before the day of the spectro- 

 scope all speculation upon the chemistry of the stars was in vain; 

 with its advent the material unity of planets, suns, and nebulae was 

 made clear. To the astronomer, a new eye was given; to the 

 chemist, a new laboratory. Three sciences were brought to a 

 single focus, and each one gained in power thereby. 



In its application to what may be called chemical astronomy^ 

 one achievement of the spectroscope was particularly notable — 

 namely, the rehabilitation of the nebular hypothesis. When the 

 gigantic telescope of Lord Rosse had resolved some nebula3 into- 

 clusters of stars, it was thought that all other nebulae might be of 

 the same character; the visible basis of the hypothesis was gone. 

 But the spectroscope soon found among these celestial objects some 

 which were truly clouds of incandescent gas, and so the nebular 

 hypothesis received a new standing, becoming stronger than ever 

 before. One point, however, was strange: these gaseous clouds 

 were of the simplest composition; hydrogen and nitrogen were 

 their chief constituents; how, then, could a world like ours origi- 

 nate from them? 



Further investigation, to which Iluggins and Secchi were the 

 chief contributors, showed, however, that from nebula to planet 

 there is a regular, progressive order of chemical complexity. The 

 nebula3 are simple; in the hotter stars a few more elements ap- 

 pear; more still can be detected in colored stars and the sun; but 

 the planets, represented by our earth, are most complex of all. So 

 far the facts; the scientific imagination now comes into play. If 

 suns and planets were derived -by a process of condensation from 

 such nebula3 as exist to-day, perhaps the process of evolution was 

 attended by an evolution of the chemical elements themselves. 



